Crane controls

ABSTRACT

A control for a crane boom mounted on a self-propelled vehicle for pivotable movement about vertical and horizontal axes, the control including first control means for controlling boom movement about a horizontal axis and second control means for controlling boom extension. Connecting means cooperating with said first and second control means are provided for actuating one of said first and second control means upon actuation of the other to maintain the free end of the boom in a predetermined vertical or horizontal plane. Vehicle orientation compensating means also may be included, as well as ground level reference means to reference the boom relative to a remote point.

United States Patent [191 Brownell et al.

[54] CRANE CONTROLS [75] Inventors: Roy D. Brownell, Aurora; Richard E.Rogers, Oswego, both of I11.

[73] Assignee: Clark Equipment Buchanon', Mich.

[22] Filed: Mar. 1, 1971 [21] Appl. No.: 119,663

Company,

Related US. Application Data [63] Continuation-impart of Ser. No.794,042, Jan. 27,

[56] References Cited UNITED STATES PATENTS 3,265,220 8/1966 Knight ..21 2/39 [4 1 May 29, 1973 [5 7] ABSTRACT A control for a crane boommounted on a selfpropelled vehicle for pivotable movement about verticaland horizontal axes, the control including first control'means forcontrolling boom movement about a horizontal axis and second controlmeans for controlling boom extension. Connecting means cooperating withsaid first and second control means are provided for actuating one ofsaid first and second control means upon actuation of the other tomaintain the free end of the boom in a predetermined vertical orhorizontal plane. Vehicle orientation compensating means also may beincluded, as well as ground level reference means to reference the boomrelative to a remote point.

10 Claims, 5 Drawing Figures PAIENIEWZ 3.735.876

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SHEET a 0F 4 ROY D. BRO NELL RICHARD EROGERS CRANE CONTROLS This is inpart a continuation of co-pending application Ser. No. 794,042 entitledIMPROVEMENTS IN CRANE CONTROLS filed Jan. 27, 1969.

BACKGROUND OF THE INVENTION This invention relates to cranes and moreparticularly to controls for automatically controlling the orientationof crane booms.

In Applicants copending application entitled Improvements in TreeHarvesting filed Jan. 27, 1969 a novel control mechanism is disclosedwhich, although described in connection with controlling the orientationof a boom supported tree harvester, has significant applicability tocranes in general. In crane operation, it is sometimes desirable toassure that the free end of the crane or load is maintained in, or doesnot exceed a predetermined elevation relative to some point remote fromthe crane. Although automatic controls have heretofore been provided tolimit boom elevation or working radius to assure stable or safe craneoperation, these controls are not generally satisfactory for maintainingor restricting the movement of the free end of a boom to a predeterminedplane referenced to a remote point. This is because the prior artcontrols have not included suitable means to establish and compensatefor all the variables which may be determinative of relative boomorientation, such as boom angle, boom length, vehicle orientation, andrelative location of a remote point which is to be utilized as areference or bench mark.

BRIEF DESCRIPTION OF THE INVENTION In this light, the present inventionprovides a control for a crane boom pivotally supported on a vehicle formovement about vertical and horizontal axes, the control including firstcontrol means for controlling boom elevation movement about thehorizontal axis and sec ond control means for controlling boomextension. Connecting means cooperating with the first and secondcontrol means upon actuation of the other for maintaining the free endof the boom in a predetermined plane. The control may further includevehicle orientation compensation means for compensating for vehiclemisorientation and reference means for referencing the boom relative toany point within its working radius.

BRIEF DESCRIPTION OF THE DRAWINGS A more thorough understanding of oneembodiment of the present invention may be gained by reference to theaccompanying drawings wherein:

FIG. 1 is a schematic elevational view of a selfpropelled craneincluding one embodiment of a boom control according to the presentinvention;

FIG. 2 is a schematic fragmentary side view one embodiment of the cranecontrol shown in F IG. 1; and

FIG. 3 is a schematic fragmentary front view of a portion of the cranecontrol shown in FIG. 2.

FIG. 4 is a schematic drawing of electrical circuitry for the operationof the device;

FIG. 5 is a schematic fragmentation side view of a second embodiment ofthe crane control shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION Referring in more detail to FIG. 1of the drawings, a control according to the present invention is adaptedfor use on a conventional mobile, selfpropelled crane 10. The crane 10includes a motorized wheeled vehicle 12 on which is supported alongitudinally extensible boom assembly 14 mounted for pivotablemovement about vertical and horizontal axes. The boom assembly 14comprises the base section 16 pivotally connected to a boom support 18for pivotal movement about a horizontally disposed pivot pin 20. Anextensible fluid motor 22 is connected between the boom base section 16and the boom support 18 for pivotally moving the boom assembly 14 in avertical direction. The boom support 18 is pivotally connected to thevehicle 10 for pivotal movement about a vertical axis which may beeffected by a rotary fluid motor, not shown. The boom assembly 14further includes at least first and second extensible sections 24 and 26telescopically received in the base section 16 and adapted to belongitudinally extended or retracted by extensible fluid motors, notshown. On the outer end of the second extensible section 26, a fixedsheave block 28 is provided over which a cable 30 is threaded forsuspending a moving sheave block 32 supporting a load engaging hook 34.A conventional manually operable fluid control, not shown, is providedfor controlling boom movement about the horizontal axis and forcontrolling longitudinal extension of the boom.

To maintain the free end of the boom assembly 14 in a predeterminedplane, in spite of contrary actuation of the manually operable boomcontrol, the present invention provides a unique boom control assembly35 which will now be discussed.

With reference to FIG. 2 of the drawings, the basic components of theboom control assembly 35 may be summarized as follows. A boom elevationand length follower assembly 42 which is automatically moveable inaccordance with vertical pivoting and extension or retraction of theboom assembly 14 is provided to read boom movement. Movement of thefollower assembly causes corresponding movement of a switch bar assembly40 which is spring-loaded to the boom up condition and which isconnected to the manually operable boom fluid motor control. Anelevation stop pin bank assembly 38 is selectively adjustable to limitboom height to a predetermined elevation by limiting movement of theswitch bar assembly 42 and thereby controlling actuation thereof. Topermit referencing or indexing the control to any point within theworking radius which is to serve as a bench mark from which boommovement may be gaged, an elevation referencing assembly 43 is provided.Additionally, to compensate for fore and aft misalignment of thevehicle, a vehicle orientation compensating linkage assembly 36 isincluded. These assemblies are mounted in a housing 39 which may includea hinge door to provide access thereto.

More specifically, the vehicle orientation compensating linkage assembly36 comprises a first vertical link 44, the upper end of which ispivotally connected by an upper pivot pin 45 to the housing 39. An upperhorizontal link 46 is pivotally mounted on the upper pivot pin 45 and alower horizontal link 47 is pivotally mounted on a lower pivot pin 48pivotally connected to the lower end of the first vertical link 44. Theupper horizontal link 46 is provided with a lateral extension 50, thefree end of which supports a spring 54. A first ear 56 extends from onelateral side intermediate the length of the vertical link 44, the ear 56overlapping a second ear 58 fixed intermediate the length ofa secondvertical link 60. A vehicle orientation compensating motor 68 ispivotally supported on the housing 39 for rotating a threaded shaft 70in either rotary direction. The free end of the shaft 70 is connected tothe first vertical link 44. A conventional orientation responsive gageand mercury switch 72 is mounted on the vertical link 44 for actuationof the motor 68.

An appropriate circuitry for the actuating of motor 68 is shown in FIG.4. Lead 91 from a power source such as a battery 61 connects to bothends 64 and 65 of switch 72 which contains mercury 200. Lead 93 out ofend 64 of switch 72 is connected to the coil of relay 62 and lead 95 outof end 65 is connected to the coil of relay 63. Lead 97 completes thecircuit between the coils of relays 62 and 63 and battery 61.Misorientation of link 44 which causes mercury 200 to complete thecircuit of end 64 of switch 72 will energize relay 62. Similarly,misorientation of link 44 which causes mercury 200 to complete thecircuit of end 65 will energize relay 63. Relay 62 operates a doublepole switch 107 which connects leads 97 and 99 from battery 61 to poles103 and 101 respectively of motor 68. Relay 63 operates a similar doublepole switch 109 which connects leads 97 and 99 to poles 103 and 101 inthe reverse order of switch 107. Consequently, actuation of one end ofswitch 72 will connect motor 68 to battery 61 to operate motor 68 in onedirection and actuation of the other end of switch 72 will reverse thepolarity of the battery 61 to operate motor 68 in the oppositedirection.

Returning now to FIG. 2, it can be seen that orientation of the vehicle12 in an unlevel fore and aft condition induces the vertical link 44 toassume a vertically inclined position. Such an inclined position causesthe mercury switch 72 to actuate the motor 68 to move the threaded shaft70 in an appropriate direction to return the vertical link to anabsolutely vertical condition. A pair of maximum vehicle misorientationelectric switches 74 and 76 are positioned in the extremities of thepath of swinging movement of the vertical link 44 whereby, upon contactwith the link, the switches may actuate a warning device, such as light111 to indicate an extreme or impractical orientation for operating thecrane 10. A circuit whereby the operation of either switch 74 or 76 willpermit a current to flow between battery 61 and light 11 l is clearlyshown in FIG. 4 such that further explanation is unnecessary.

The maximum elevation stop pin bank assembly 38 permits the craneoperator to select an elevational plane which the free end of the boomassembly is to be maintained. The bank assembly 38 is mounted on thesecond vertical link 60 and comprises a bank housing 78 in which aplurality of equally vertically spaced, r arwardly extending stop pins80 are mounted. Upper and lower stop pins 81 and 83 are fixedly mountedin the housing 78 and establish the upper and lower limits of boommovement at one reference point. Ten moveable stop pins 82 are provided,each corresponding to a boom elevation somewhere between allowableextremes and each being adapted to be moved from a retracted position,shown in full lines in FIG. 3, to an extended position shown in phantomlines by an individual stop pin solenoid 84 selectively operable by theoperator of the vehicle 12. The number of stop pins may be varied asdesired to provide any number of boom operational planes. Of course,other stop arrangements, such as a one including a single moveable stoppin of an adjustable elevation, may be alternately utilized whichprovide any desired increment of stop adjustment.

The switch bar assembly 40 which follows movement of the boom followerassembly 42, comprises second upper and lower horizontal links 85 and86, the inner ends of which are pivotally connected on the upper andlower pivot pins 45 and 48, respectively. The inner ends of the secondlower horizontal link 86 is provided with an extension 87 connected tothe extension 50 on the first upper horizontal link 46 by the spring 54whereby the stop pin bank 38 is urged to rotate upwardly or in aclockwise direction as shown in FIG. 2 and the switch bar assembly 40 isurged downwardly or in a counterclockwise direction. Connected betweenthe outer ends of the second upper and lower horizontal links 85 and 86by pivot pins 92 and 94 is a third vertical link 90. With reference toFIG. 3 of the drawings, from the rear face of the third vertical link90, a switch pivot ear 98 projects. A horizontal pivot or switch arm 100is pivotally connected to the ear 98 by of horizontal pivot pin 102 anda horizontally extending bar 104 is fixed in a perpendicular relation tothe rear end fo the pivot arm 100. On the front face of the thirdvertical link 90, a triangular projection 105 is provided to the frontend of which a laterally extending, horizontal arm 106 is fixed toextend laterally into the path of the stop pins 80. Fixedly positioned,the front face of the third vertical link 90 in the path of pivotalmovement of the switch arm 100, is a pair of upper and lower switches108 and 1 10 for activating the boom fluid control, which may be of aconventional electrohydraulic type for controlling movement of the boomhoist cylinder 22. Circuitry for these switches is shown in FIG. 4 andwill be explained later. A spring 112 connects the horizontal bar 104and the lower end of the link 90 to urge the horizontal arm 106 in acounterclockwise direction, as shown in FIG. 3, to thereby actuate theupper switch 108. It is seen that the control 35, when activated, isnormally in the boom up position.

As can be seen in FIG. 4, the boom hoist cylinder 22 is extended byenergizing solenoid 137A to operate hydraulic valve 137 to allowpressurized fluid from a source such as a pump (not shown) to enter thebase 22A of cylinder 22 through line 135. The solenoid 137A of valve 137is connected to battery 61 by leads 139, 141 and 143 through relay 145.Relay 145 may include a double pole double throw switch adapted to lockout manual controls which might conflict the operation of the device byopening the circuit between lines 147 and 149. The solenoid of relay 145is connected to battery 61 through switch 108 by means of lines 151, 153and 155. Closing switch 108 breaks the circuit between lines 147 and 149and allows pressurized fluid to flow through line 135 extending cylinder22 and elevating the boom. Conversly, cylinder 22 is retracted byenergizing solenoid 1378 to allow pressurized fluid to enter the rod end228 of cylinder 22 through line 136. Valve 138 is connected to battery61 through relay 146 by leads 140, 142 and 144. Relay 146 also includesa double pole double throw switch for opening the circuit between lines148 and 150 while closing the circuit to solenoid 1373 to lock outconflicting manual controls. Leads 152, 154 and 156 connect the coil ofrelay 146 through switch 110 to battery 61 such that actuation of switch110 open the circuit between leads 148 and 150 and simultaneously allowspressurized fluid to flow through line 136 to lower the boom.

The boom elevation and length follower assembly 42 shown in FIG. 3comprises a spring-tensioned cable drum assembly 114 adapted to extendor retract a threaded shaft 118 in accordance with extension or retraction of the boom assembly 14. The cable drum as sembly 114 comprisesa cylindrical housing 115 in which is positioned a cable drum 116 whichthreadedly receives the threaded shaft 118. A helical spring 117 urgesthe drum 116 to reel in a cable 119 reaved thereabout. The free end ofthe cable 119 is connected to the fixed block 28 on the secondextensible section 2.6 of the boom assembly 14 whereby extension of theboom assembly moves the threaded shaft 118 towards the left, as shown inFIG. 2, and retraction of the boom assembly moves the threaded shaft 118towards the right. The cylindrical housing 115 is fixedly connected tothe lower end of support 124. The upper end of the support 124 ispivotally mounted through the boom pivot pin 20 so that the housing. 115pivots around the horizontal axis in accordance with the pivotalmovement through a vertical plane of the boom assembly 14. On the outerend of the threaded shaft 118 is a vertical leg 126. A roller 128 isrotatably mounted on the upper end of the vertical leg 126 by a rollerpin 130 and contacts the horizontal bar 104 at a point somewhere alongits length. It should be noted that the roller 128 moves horizontallyand vertically in accordance with movement of the fixed sheave block 28and carries the horizontal bar 104 of the switch assembly 40 along withsuch movement.

The elevation referencing assembly 43 comprises a referencing locksolenoid 132 positioned on the front face of the second ear 58 providedon the second vertical link 60. A friction element or surface 134 isprovided on the rear face of the solenoid 132, the element beingspring-loaded into engagement with a cooperating friction element 136 oron the front face of the first ear 56 on the first vertical link 44. Inthis manner, the first and second vertical links 44 and 60 are normallylocked together. However, when it is desired to reference the control toany point within the working radius of the boom assembly 14, thesolenoid 132 may be actuated to overcome the spring load urgingengagement of the friction elements to thereby free the second verticallink 60 for movement relative to the first vertical link 44. It shouldbe apparent that any movement of vertical link 60 will be independent ofthe movement follower assembly 42 unless switch bar assembly 40 engagesa pin stop of assembly 38.

Operation of the control assembly 35 according to the present inventionis as follows. Assuming the crane is positioned so that the vehicle 12is oriented in an unlevel position from front to rear. This unlevelcondition is sensed by the mercury switch 72 on the first vertical link44 and the vehicle orientation compensating motor is accordinglyactuated to return the first vertical link 44 to an absolute verticalcondition. In this manner, the control assembly 35 is positioned in abase condition independent of vehicle orientation. Of course, if extremeadjustment of the first vertical link 44 is required to compensate foran extremely unlevel condition of the vehicle, the first vertical link44 will be moved to a point wherein it actuates either of the maximumvehicle misorientation switches 74 and 76. A warning signal may therebybe actuated to indicate an impractical vehicle orientation necessitatingvehicle relocation.

With the control 35 deactivated or placed in a condition wherein it willnot oppose operation of the boom manual fluid control, the boom assembly14 is moved by manual actuation of its fluid control until the fixedsheave block 28 is vertically aligned with a remote reference pointwhich is to serve as a bench mark. Usually this point will correspond toground level at some location within the working radius which, ofcourse, may differ in elevation from ground level at the vehicle or theground level roller at the preceding orientation of the vehicle Theroller 128 is now referenced to ground level since its vertical positionalways proportionately corresponds to the vertical position of sheaveblock 28. Ground level referencing of the overall control isaccomplished as follows. The brake solenoid 132 is activated to overcomethe spring load urging engagement of the brake surfaces 134 and 136 onthe first and second ears 56 and 58 on the first and second verticallinks 44 and 60 thereby freeing the stop pin bank assembly 38 and theswitch bar assembly 40 for independent movement relative to the firstlink 44. The stop pin bank assembly 38 and the switch bar assembly 40are allowed to rotate either in a clockwise or a counterclockwisedirection, depending upon preceding ground reference, until the actionof spring 54 on the extension 50 of the upper parallel link 46 andon theextension 87 of the lower parallel link 86 urges the horizontal arm 106to contact the lower stop pin 83. Simultaneously, the combined weightsof these units, reduced partially by the action of spring 54 onextension 50, provides the force required to establish contact betweenthe horizontal bar 106 and roller 128. The brake solenoid 132 isdeactivated thereby permitting the spring loaded brake surface to returnto engagement to lock together the first and second vertical links 44and 60. At this point, the linkage is locked in a position referenced toground level at the selected point. The operator then actuates anappropriate one of the pin solenoids 84 to move the associated pin 82 tothe extended position, shown in phantom lines in FIG. 3, to therebylimit upward movement of the fixed sheave block to a selected planebetween boom movement extremes, a desired distance above ground levelelevation of the reference point.

The vehicle operator may then activate the control 35 to override theboom manual fluid control. Because the horizontal bar 104 is springloaded to actuated the upper or boom up switch 108, theboom isautomatically raised and such upward movement is continuedv until theroller 128 carries the spring loaded horizontal bar 104 to an elevationwherein the horizontal arm 106 contacts the extended stop pin 82. Anyextension or elevation of boom assembly 14 which tends to move arm" 106relative to pin stop 82 will then actuate one of the switches 108 and110 such that there is a fixed relationship between the position of stoppin 82 of assembly 38 and the plane or other complex path in which theboom is to be maintained. Further upward pivoting of the boom assembly14 and consequential movement of the elevation follower 42 causes thepivot arm to pivot in a clockwise direction (as shown in FIG. 3) aboutpivot pin 102 against the action of the spring 112 to thereby actuatethe lower ofboom down switch 110. Slight downward movement will occuruntil the boom is oriented as desired with the free end thereof in thepreselected plane. Manual operation of the boom manual fluid control tocause further upward movement by either boom angling or extension causesupward movement of the elevation follower roller 128. However, evenslight upward movement of the roller 128 causes the lower of boom downswitch 110 to be automatically activated thereby reversing manualcontrol. In this manner, the free end of the boom is maintained in thedesired plane. It should be noted that actuation of boom manual fluidcontrol to effect elongation of the boom assembly causes compensatingdownward adjustment of boom angle. Consequently, the free end of theboomis moved in uni-planar forwardly direction thereby providing a levelcrowd" feature which is particularly advantageous in some craneoperations.

The disclosed control is easily modifiable to maintain the free end ofthe boom in a predetermined curve or complex path. To achieve theseends, it is merely necessary to shape the underside of the horizontalbar 104 to proportionately conform to the desired path. Suchmodification may be desirable when utilization of a crane in a confinedarea wherein the vertical or lateral limits of operating space areinconstant or defined by more than one simple horizontal or verticalplane.

Although utilization of one embodiment of the control assembly 35 hasheretofore been described for maintaining the free end of a boom in apreselected horizontal plane, it should be noted that the controlassembly may be modified to maintain the free end of a boom within otherlimitations such as a preselected vertical plane. Such may beaccomplished merely by reorienting the control to impose the limitationsdesired. FIG. shows a modification which would enable the control tomaintain a constant boom radius which may be beneficial for exactrepositioning of loads and to permit the vertical lifting of loads. Therefencing mechanism would permit the positioning of loads relative to achosen reference point.

As seen in FIG. 5, switch bar assembly 160 consists of a vertical bar196 mounted on horizontal link 162. These two elements correspond to bar104 and link 90 respectively as discussed with respect to the embodimentshown in FIG. 2. The mounting of bar 196 to link 162 is similar to themounting of bar 104 to link 90 such that bar 196 may move horizontallyrelative to link 162 to actuate one of two switch 192 and 193. Link 162is pivotally connected at one end to link 163 and at the other end tolink 164. Each of links 163 and 164 are pivotally connected to one endof link 170. Extension 165 oflink 164 is urged to the left by spring 168such that switch bar assembly 160 is urged to the right to engage roller184 of the boom extension and elevation following assembly 180.

The stop pin bank assembly 175, having stops 197, 198 and 199 is mountedon horizontal bar 171 which is maintained parallel to link 170 by pivotlinks 173 and 174. Links 170, 173, 171 and 174 form a parallelogram topermit horizontal referencing of the stop pin bank assembly 175. Spring168 is connected to extension 176 of link 173 and urges the stop pinbank assembly 175 to the left. Solenoid 185 permits thelocking ofparallelogram 170, 173, 171 and 174 against further movement after thestop pin bank assembly 175 has been referenced. Mercury switch controlsmotor 191 to maintain the horizontal orientation of link 170 duringmisorientation of the vehicle.

The boom follower assembly 180 is pivoted with the boom at pivot pin187. Cable 119 is reaved about spool 182 such that extension orretraction of the boom assembly 14 cause rotation of the spool 182.Spool 182 threadedly engages threaded shaft 183 such that rotation ofspool 182 causes movement of threaded shaft 183 responsive to boomextension or retraction. Roller 184 is provided at the end of threadedshaft 183 to engage vertical bar 196 of the switch bar assembly 160.Switch bar assembly 160 also includes arm 194 for engaging the stops ofthe stop pin bank assembly 175. Switches 192 and 193 are actuated bymovement of bar 196 relative to link 162 as switches 108 and 110 areactuated by movement of bar 104 relative to link 90 in FIG. 2. Switch192 actuates boom extension and switch .193 actuates boom retraction.Spring 195 urges bar 196 to the right. The device is pivotally mountedto the housing 39 at point 181.

The operation of the assembly shown in FIG. 5 is substantially the sameas the device shown in FIG. 2. Spring 168 acts to maintain bar 196 ofthe switch bar assembly 160 in contact with roller 184 of the boommovement follower assembly 180. Spring 195 actuates switch 192 toinitiate extension of the boom assembly 14. Extension of the boomassembly 14 extends cable 119 and rotates spool 182 to extend threadedshaft 183. Boom extension continues until arm 194 of switch bar assembly160 engages an extended pin 198 on switch bar assembly 175. Furtherextension of shaft 183 causes bar 196 to move relative to link 162 todeactivate switch 192 and terminate boom extension. Any manual change inboom extension or boom elevation which changes working radius will tendto move bar 196 relative to pin 198 and thereby actuate one of theswitches 192 and 193. Actuation of one of the switches 192 and 193 willcause boom extension or retraction as needed to maintain a desiredworking radius.

Additionally, although the present invention has been described in acrane control environment, it should be apparent that the basic conceptthereof is applicable to a crane boom movement indicator wherein controlfeatures are replaced by warning signals.

Further, various novel aspects of the present invention, alone or incombination, may be advantageously included in a crane boom controlwherein conventional means are provided to read line load andaccordingly control boom orientation to circumvent vehicle tipping, boomdamage or line failure or unsafe loads in general.

Finally, although but two embodiments of the present invention have beendisclosed, should be appreciated that various mechanical modificationsor substitutions may be made without departing from the basic inventiveconcepts thereof to be ascertained from the following claims.

We claim:

1. A control device for a material handling apparatus including anextensible boom pivotally mounted for movement about horizontal andvertical axes, the device for controlling the boom movement within apredetermined complex path, the control device including:

first control means for controlling boom movement about the horizontalaxis,

second control means for controlling boom extension,

a boom movement follower moveable according to movement of the boomabout said vertical and horizontal axes,

a stop fixedly positioned relative to said complex path,

a first element engageable with said stop and responsive to movement ofsaid boom movement follower,

a switch for actuating one of said first and second control means,

said first element being adapted to actuate said switch upon movement ofsaid boom and said boom movement follower which tends to move said firstelement relative to said stop, and

further including a bar moveably mounted on said first element andengageable with said boom movement follower,

wherein said bar has a first surface shaped to proportionately conformto the shape of said complex path, and adapted to engage said boommovement follower.

2. A control device for material handling apparatus including anextensible boom pivotally mounted for movement about horizontal andvertical axes, a device for controlling boom movement within apredetermined complex path, the control device including:

first control means for controlling boom movement about the horizontalaxis,

second control means for controlling boom extension,

a boom movement follower moveable according to movement of the boomabout said vertical and horizontal axes,

a stop fixedly positioned relative to said complex path,

a first element engageable with said stop and responsive to movement ofsaid boom movement follower,

a switch for actuating one of said first and second control means,

said first element being adapted to actuate said switch upon movement ofsaid boom and said boom movement follower which tends to move said firstelement relative to said stop, and

further comprising a second element, said stop mounted on said secondelement, said second element moveable relative to said first element,means for referencing said second element and said stop to a pointremote from the boom, and means for locking said second element againstmovement away from said reference position.

3. A control device for a material handling apparatus according to claim7 wherein the movement of said first element is substantially parallelto the movement of said second moveable element.

4. A control device for a material handling apparatus according to claim8 and further including a bar, said bar moveably supported on said firstelement, said bar engageable with said boom movement follower.

5. In a control device for a material handling apparatus including anextendible boom pivotally mounted for movement about horizontal andvertical axes, the control device including a boom movement followermoveable in accordance with the vertical and longitudinal movement ofthe boom, the improvement comprising a first element moveableindependent of the movement of the boom movement follower, a stopmounted on said first element, means for referencing said first elementand said stop to a point remote from the boom, means forlocking saidfirst element against further movement, said boom movement followercooperating with said stop to provide a signal responsive to boommovement relative to said remote point.

6. In a control device for a material handling apparatus according toclaim 5 wherein said device includes a second element, said secondelement moveable responsive to said boom movement follower and adaptedto engage said stop.

7. In a control device for a material handling apparatus according toclaim 11 wherein said device further includes a switch, said switchbeing actuated upon movement of said boom movement follower which tendsto move said second element relative to said stop.

8. In a control device for a material handling apparatus according toclaim 10 wherein said said boom is mounted on a vehicle and said devicefurther includes boom orientation means cooperating with said firstelement to compensate for misorientation of the vehicle.

9. In a control device for a material handling apparatus according toclaim 8 wherein said boom orientation means is adapted to maintain saidfirst element in a substantially horizontal orientation duringmisorientation of said vehicle.

10. In a control device for a material handling apparatus according toclaim 13 wherein said boom orientation means is adapted to maintain saidfirst element in a substantially vertical orientation duringmisorientation of said vehicle.

1. A control device for a material handling apparatus including anextensible boom pivotally mounted for movement about horizontal andvertical axes, the device for controlling the boom movement within apredetermined complex path, the control device including: first controlmeans for controlling boom movement about the horizontal axis, secondcontrol means for controlling boom extension, a boom movement followermoveable according to movement of the boom about said vertical andhorizontal axes, a stop fixedly positioned relative to said complexpath, a first element engageable with said stop and responsive tomovement of said boom movement follower, a switch for actuating one ofsaid first and second control means, said first element being adapted toactuate said switch upon movement of said boom and said boom movementfollower which tends to move said first element relative to said stop,and further including a bar moveably mounted on said first element andengageable with said boom movement follower, wherein said bar has afirst surface shaped to proportionately conform to the shape of saidcomplex path, and adapted to engage said boom movement follower.
 2. Acontrol device for material handling apparatus including an extensibleboom pivotally mounted for movement about horizontal and vertical axes,a device for controlling boom movement within a predetermined complexpath, the control device including: first control means for controllingboom movement about the horizontal axis, second control means forcontrolling boom extension, a boom movement follower moveable accordingto movement of the boom about said vertical and horizontal axes, a stopfixedly positioned relative to said complex path, a first elementengageable with said stop and responsive to movement of said boommovement follower, a switch for actuating one of said first and secondcontrol means, said first element being adapted to actuate said switchupon movement of said boom and said boom movement follower which tendsto move said first element relative to said stop, and further comprisinga second element, said stop mounted on said second element, said secondelement moveable relative to said first element, means for referencingsaid second element and said stop to a point remote from the boom, andmeans for locking said second element against movement away from saidreference position.
 3. A control device for a material handlingapparatus according to claim 7 wherein the movement of said firstelement is substantially parallel to the movement of said secondmoveable element.
 4. A control device for a material handling apparatusaccording to claim 8 and further including a bar, said bar moveablysupported on said first element, said bar engageable with said boommovement follower.
 5. In a control device for a material handlingapparatus including an extendible boom pivotally mounted for movementabout horizontal and vertical axes, the control device including a boommovement follower moveable in accordance with the vertical andlongitudinal movement of the boom, the improvement comprising a firstelement moveable independent of the movement of the boom movementfollower, a stop mounted on said first element, means for referencingsaid first element and said stop to a point remote from the boom, meansforlocking said first element against further movement, said boommovement follower cooperating with said stop to provide a signalresponsive to boom movement relative to said remote point.
 6. In acontrol device for a material handling apparatus according to claim 5wherein said device includes a seCond element, said second elementmoveable responsive to said boom movement follower and adapted to engagesaid stop.
 7. In a control device for a material handling apparatusaccording to claim 11 wherein said device further includes a switch,said switch being actuated upon movement of said boom movement followerwhich tends to move said second element relative to said stop.
 8. In acontrol device for a material handling apparatus according to claim 10wherein said said boom is mounted on a vehicle and said device furtherincludes boom orientation means cooperating with said first element tocompensate for misorientation of the vehicle.
 9. In a control device fora material handling apparatus according to claim 8 wherein said boomorientation means is adapted to maintain said first element in asubstantially horizontal orientation during misorientation of saidvehicle.
 10. In a control device for a material handling apparatusaccording to claim 13 wherein said boom orientation means is adapted tomaintain said first element in a substantially vertical orientationduring misorientation of said vehicle.